Air actuated valve system with seismic controller

ABSTRACT

An air actuated valve system for shutting off fluid flow in a fluid conduit includes a seismic valve disposed in a seismic air circuit which is coupled to a primary air circuit. The primary air circuit delivers air at a high pressure to an air driven actuator which maintains a shut off valve in a fluid conduit in an open position. The high air pressure flows through an air switch which is operationally open and coupled to the seismic air circuit such that when the seismic valve is closed a pilot air pressure is prevented from flowing to the air switch. In the absence of the pilot air pressure, air pressure is bled from the air switch, causing the air switch to move from an open to a closed position, thus preventing air from flowing to the air actuator.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to fluid activated valvesystems, and more particularly, to an air actuated valve system havingan integrated seismic control circuit.

2. Description of the Related Art

Seismic valves which are used to shut off fluid flow upon experiencing apredetermined level of seismic activity are generally known. Where thereis a high probability of seismic disturbances, such as earthquakes,seismic valves are necessary to prevent the release of hazardous and/orflammable substances such as natural gas and LPG.

One such seismic valve is described in U.S. Pat. No. 4,745,939 to Greeret al. The seismic valve is a pin supported gate valve having agas-tight reset system. The seismic sensing component of the valveactuates shut off means when subjected to a predetermined amount andtype of horizontal sinusoidal oscillation.

Although the seismic valve described above is effective for shutting offfluid flow, the valve is normally installed in a gas line between ameter and an associated structure. Due to the placement of the seismicvalve directly in the fluid conduit, limitations are imposed upon thesize of the conduit and the type of materials handled by the conduit.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an air actuated valvesystems which is controlled by a seismic valve.

Another object of the present invention is to control a shut off valvedisposed in a fluid conduit with a seismically actuated air switch.

In a preferred embodiment, an air actuated valve system for shutting offfluid flow in fluid conduit includes a fluid shut off valve forplacement in the fluid conduit, an air driven actuator, connected to thefluid shut off valve, for moving the fluid shut off valve between openand closed positions, a primary air circuit, in fluid communication withthe air driven actuator, for supplying air to the air driven actuator ata pressure sufficient to maintain the fluid shut off valve in the openposition, an air switch disposed in the primary air circuit upstream ofthe air driven actuator and being movable between open and closedpositions, and seismic control means, connected to the air switch, forshutting off air to the air driven actuator in response to apredetermined level of seismic activity.

Preferably, the seismic control means includes a seismic air circuit, influid communication with the primary air circuit and the air switch, forsupplying air to the air switch at a pressure sufficient to maintain theair switch in the open position, and a seismic valve disposed in theseismic air circuit for shutting off air supplied to the air switch inresponse to a predetermined level of seismic activity, thereby causingthe air switch to close and thus the shut off valve to close.

These objects, together with other objects and advantages which will besubsequently apparent reside in the details of construction andoperation of the air actuated valve system as more fully hereinafterdescribed and claimed, reference being had to the accompanying drawingsforming a part hereof, wherein like reference numerals refer to likeparts throughout.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an air actuated valve system according tothe present invention;

FIG. 2 is a schematic, cross-sectional view, illustrating an air drivenactuator used in the system of claim 1; and

FIGS. 3a and 3b are schematic, cross-sectional views illustrating an airswitch used in the system of FIG. 1 in the open and closed positions,respectively.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIG. 1, an air actuated valve system according to thepresent invention is generally referred to by the numeral 10. The system10 includes an air source 12, such as an air compressor and storagetank. The air compressor is selected to provide a continuous air supplyof about 100-200 psi. This pressure is regulated by a high pressureregulator 14 to reduce the pressure from the air source 12 to about80-100 psi. Compressed air, preferably at about 90 psi is continuouslysupplied through pneumatic conduit from the air source 12, through theregulator 14 to an air driven actuator 16 coupled to a fluid shut offvalve 18 movable in a fluid conduit 20.

The air driven actuator 16 is of a spring-return type in which airpressure coming into the actuator opposes a spring force which normallybiases the valve 18 in a closed position. When air enters the actuator16 at a sufficient level of pressure to overcome the spring force, anelement, such as a shaft, within the actuator 16 is driven by the airpressure to rotate or otherwise move the valve 18 from a closed positionto an open position. Thus, as long as the actuator 16 is supplied withair at a pressure level sufficient to overcome the spring force, thefluid shut off valve 18 will be maintained in an open position. When theair pressure is removed, the valve 18 closes due to the spring force.Air driven actuators of this type are generally known and commerciallyavailable. An example is a series 39 spring-return actuator sold byWorcester Controls, Marlborough, Mass.

The high pressure regulator 14 is equipped with a gauge 15 which is usedto monitor the regulated air pressure.

The air source 12, the high pressure regulator 14 and the pneumaticconduit which connects the air source and regulator to the air actuator16 constitute a primary air circuit which communicates air from thesource 12 to the air driven actuator 16 at high pressure. An air switch22, which acts as a control valve, is disposed in the primary aircircuit upstream of the air driven actuator 16 and downstream of thehigh pressure regulator 14. The air switch 22 is movable between openand closed positions by seismic control means which shuts off air to theair driven actuator 16 in response to a predetermined level of seismicactivity. Basically, the seismic control means actuates the air switch22, shutting off the supply of air in the primary air circuit to the airdrive actuator 16.

The seismic control means includes a seismic air circuit, in fluidcommunication with the primary air circuit, which receives air from thehigh pressure regulator 14 and delivers a "pilot" air pressure to theair switch 22. A low pressure regulator or pilot regulator 24 reducesthe pressure in the seismic air circuit to about 10-15 psi. A gauge 26is coupled to the pilot regulator to faciliate monitoring of pilotpressure.

A seismic valve 28 allows pilot air pressure to flow through pneumaticconduit to the air switch 22. In the presence of a predetermined levelof seismic activity, the seismic valve is actuated to shut off the flowof pilot air to the air switch 22, thereby causing the air switch toswitch from an ON position to an OFF position to prevent air in theprimary air circuit from flowing to the air actuator 16. A bleed port 30is disposed between the seismic valve 28 and the air switch 22 such thatwhen the seismic valve closes, the bleed port 30 depletes the pilotpressure applied to the air switch 22, thereby de-activating the airswitch which, in turn, shuts off the shut off valve 18.

An electrical component of the system includes a warning indicator whichindicates failure of an external air supply or air compressor. Thereserve in the air source 12, such as an air tank, will graduallydecrease due to the small bleed port 30. An OK light 32 is illuminiatedon a front panel so long as sufficient air pressure remains in theprimary air circuit. The air actuator 16 can continue to hold the shutoff valve 18 in an open position until the pressure drops to apredetermined level as, for example, 70±30 psi. Therefore, the frontpanel includes a warning horn 34 which sounds when pressure drops belowa predetermined threshold level. Since it may take about one hour forpressure to fail to a predetermined level, this will enable theoperators to have sufficient time to correct the malfunctioning airsource.

The electrical component of the system provides local and remote alarmsboth AC and DC powered, and separate indicators notify that the systemis operational, or has a fault, such as low air supply or low battery.

A manual solenoid remote shut off 36 is coupled to a remote controlcircuit so as to provide a manual remote control shut off capability.

The electrical component further includes a trickle-charged storagebattery 38, air pressure switches 40, 42 and 44, toggle switches 1-A,1-B, 2-A, and 2-B which provide alarm control and DC power, andindicator lamps and horns for actuator of warning signals and indicatingsystem status.

Any fault in the electrical circuit, including complete power loss, willnot effect the pneumatic operation of the system. An operational alarmconnection may be made to the security or night alarm system of theinstallation site. Also, assuming system activation due to earthquake ornearby explosion, the alarms may be shut off by moving toggle switchesto their OFF position according to the following table.

                                      TABLE 1                                     __________________________________________________________________________                            1-B    1-C                                            SWITCH NUMBER    1-A    SELECT REMOTE 2-A    2-B                              FUNCTION         DC ALARM                                                                             DC ALARM                                                                             CONTROL                                                                              DC POWER                                                                             AC ALARM                         __________________________________________________________________________    TOGGLE SWITCH                                                                            TOP   ON     ON     ON     ON     ON                               POSITIONS  CENTER                                                                              OFF    OFF    OFF    OFF    OFF                                         BOTTOM                                                                              ON     OFF    ON     ON     ON                               __________________________________________________________________________

When resetting the system after a seismic event, it is preferable tofirst perform a damage and leak check of the protective area. Then, theseismic valve is reset by pulling upward on a reset ring and then downto reset the gate/actuator on its pin at the top of the chamber. Thisstructure is fully described in U.S Pat. No. 4,207,912, which isincorporated herein by reference.

An example of air driven actuator 16 and shut off valve 18 isillustrated in FIG. 2. Air under high pressure enters the actuator 16from one end thereof and, through a gear mechanism, causes a ballelement of a ball valve to rotate to the open position illustrated inFIG. 2. The gear mechanism is a piston-actuated rack and pinion gearsystem which produces a torque for rotating the valve. A spring 16aopposes piston movement imparted by air pressure such that when airpressure is removed, the spring causes the piston to return to itsoriginal position in which the ball valve is in a closed state. Anyother type of air actuator and valve combination can be used so long asa spring-return mechanism causes the valve to close when air is removed.Such an alternative embodiment may include a pneumatic actuator whichhas a piston-type assembly wherein a cam-shaped lever is driven by apiston-operated slide to produce a torque for rotating a valve throughits opening and closing cycles. This type of actuator is available fromWorcester Controls. Moreover, the penumatic actuator 16 may be used incombination with diverse types of valves such as ball valves, butterflyvalves, gate valves, etc.

FIGS. 3a and 3b illustrate an exemplary air switch 22, which is in openposition in FIG. 3a and closed in FIG. 3b. Referring to FIG. 3a, airfrom the primary air circuit, at a relatively high pressure, enters aninlet 22a of the air switch 22 and passes through an outlet 22b to theair driven actuator 16. In order for this to occur, a piston 22c isdriven from right to left by pilot air pressure from the seismic aircircuit which enters the air switch 22 from a right hand side at 22d. Aspring 22e opposes movement of the piston 22c such that when the pilotair pressure is removed, such as when the seismic valve is actuated, thespring 22e returns the piston to its normally closed positionillustrated in FIG. 3b. The piston 22c has two enlarged portions, one ofwhich seats over the inlet 22a when the piston is in its originalposition shown in FIG. 3b. An exhaust port 22f, which is closed in FIG.3a, becomes open when the spring returns the piston. Thus, incoming airunder high pressure is blocked at the inlet 22a, and air downstream ofthe air switch 22 bleeds back through the air switch out the exhaustport 22f. This type of air switch is available from Numatics ofHighland, Mich.

Although the invention has been described with respect to particularillustrative embodiments, it will be understood that variations andmodifications may be made within the true spirit and scope of thepresent invention.

What we claim is:
 1. An air actuated valve system for shutting off fluidflow in a fluid conduit, comprising:a fluid shut off valve for placementin the fluid conduit; an air driven actuator, connected to the fluidshut off valve, for moving the fluid shut off valve between open andclosed positions; a primary air circuit, in fluid communication with theair driven actuator, for supplying air to the air driven actuator at apressure sufficient to maintain the fluid shut off valve in the openposition; an air switch disposed in the primary air circuit upstream ofthe air driven actuator and being movable between open and closedpositions; and seismic control means, connected to the air switch, forshutting off air to the air driven actuator in response to apredetermined level of seismic activity, said seismic control meanscomprising: a seismic air circuit, in fluid communication with theprimary air circuit and the air switch, for supplying air to the airswitch at a pressure sufficient to maintain the air switch in the openposition, and a seismic valve disposed in the seismic air circuit forshutting off air supplied to the air switch in response to apredetermined level of seismic activity, thereby causing the air switchto close and thus the shut off valve to close.
 2. An air actuated valvesystem according to claim 1, wherein the air driven actuator has aspring-return mechanism which moves the shut off valve to the closedposition in the absence of air pressure.
 3. An air actuated valve systemaccording to claim 1, wherein the air switch includes a movable elementmovable between open and closed positions, and a spring-return mechanismfor moving the movable element to the closed position in the absence ofpilot air pressure.
 4. An air actuated valve system according to claim1, wherein the primary air circuit includes an air source, a highpressure regulator, and pneumatic conduit for connecting the air sourceto the air actuator through the high pressure regulator and through theair switch.
 5. An air activated valve system according to claim 4,wherein the primary air circuit further includes a low air pressurewarning system for indicating a condition of low air pressure in theprimary air circuit.
 6. An air actuated valve system according to claim4, wherein the seismic air circuit includes a pilot air regulator, influid communication with the high pressure regulator, for reducing airpressure from a level regulated by the high pressure regulator to alower pilot air pressure, a bleed port disposed between the seismicvalve and the air switch for bleeding off residual pilot air pressurebetween the air switch and the seismic valve upon actuator of theseismic valve which actuator interdicts the pilot air pressure to theair switch, and pneumatic conduit for connecting the pilot air regulatorto the high pressure regulator and to the seismic valve, and forconnecting the seismic valve to the air switch through the bleed port.7. An air actuated valve system according to claim 1, further comprisingan electrical component for monitoring air pressure in the valve systemand for indicating a warning signal when pressure falls to apredetermined level.
 8. An air actuated valve system according to claim7, wherein the electrical component further includes a test circuit forchecking the operational status of the air actuated valve system.